The present invention relates to a thin-film magnetic head wafer on which a plurality of thin-film magnetic head elements for magnetically recording into and/or reproducing from a magnetic medium such as a hard disk or a floppy disc are formed. The present invention also relates to a manufacturing method of a thin-film magnetic head.
In general, when fabricating thin-film magnetic heads, various wafer processes for forming many thin-film head elements on a wafer in matrix are executed. Such wafer processes contain without exception a plurality of light exposure steps that typically use an optical stepper.
When performing a light exposure step using an optical stepper, it is necessary to confirm before each exposing operation that a position of focus of an optical system in this stepper is correctly located on an image surface or image plane of the wafer and that the image plane of the wafer is horizontal to the stepper. In order to perform these focus check and leveling check, detection of distance between the stepper and the image plane of the wafer will be required.
Since each magnetic head element formed on the thin-film magnetic head wafer is very tall, there are higher differences on the surface of the magnetic head wafer than on the surface of a semiconductor wafer. In most cases, these high differences are located even in regions used for focus check and leveling check. Therefore, the focus and the leveling will be checked based upon an average level or height of several magnetic head elements. The level of the head elements formed on not only one wafer but also wafers fabricated in different lots may vary. Thus, accuracy of the focus check and the leveling check may lower, and size and shape of resist patterns formed by using the stepper may become unstable causing yields to reduce.
It should be noted that no consideration has been taken before for accurately executing focus check and leveling check when performing a light exposure with respect to a thin-film magnetic head wafer.
It is therefore an object of the present invention to provide a thin-film magnetic head wafer and a manufacturing method of a thin-film magnetic head, whereby continued accuracy in focus check and leveling check in case of an exposure process can be assured.
According to the present invention, a thin-film magnetic head wafer with a surface to be exposed by means of an optical stepper includes a plurality of thin-film magnetic head elements formed on the surface, and distance check regions that are flat in level and horizontal to the surface of the wafer, at least one of the distance check regions being formed on the surface within one exposure area of the optical stepper.
At least one of distance check regions is formed on the surface of the wafer within one exposure area of the optical stepper, and the distance check region is kept flat and horizontal to the surface of the wafer. Thus, high accuracy of the focus check and the leveling check can be maintained. As a result, size and shape of resist patterns formed by using the stepper can be kept stable resulting yields to increase.
It is preferred that the distance check regions include a region for checking focus of the optical stepper with respect to the wafer.
It is also preferred that the region for checking focus is formed only one within one exposure area of the optical stepper and/or that the region for checking focus is formed at center portion of the one exposure area of the optical stepper.
It is preferred furthermore that the distance check regions include regions for checking leveling of the wafer with respect to the optical stepper.
It is also preferred that the plurality of regions for checking leveling are formed within one exposure area of the optical stepper, and/or that the regions for checking leveling are formed at bordering portions in the one exposure area of the optical stepper.
Preferably, the regions for checking leveling are formed to be split across a boundary between the exposure area and an adjacent exposure area of the optical stepper.
It is preferred that the distance check regions have surfaces with a level equal to that of a reference surface of the wafer, or that the distance check regions have surfaces with a level equal to that of a thin-film layer or thin-film layers deposited on the reference surface of the wafer.
According to the present invention, furthermore, a manufacturing method of thin-film magnetic heads on a wafer with a surface to be exposed by means of an optical stepper, includes a step of forming distance check regions that are flat in level and horizontal to the surface of the wafer, at least one of the distance check regions being formed on the surface within one exposure area of the optical stepper, and a step of checking a distance between the optical stepper and the surface to be exposed by using at least one of the formed distance check regions.
It is preferred that the checking step includes a step of checking focus of the optical stepper with respect to the surface of the wafer by using one of the formed distance check regions, and/or that the checking step includes a step of checking leveling of the surface of the wafer with respect to the optical stepper by using of the formed distance check regions.
It is also preferred that the forming step includes a step of inhibiting formation of thin-film layer on the distance check regions so that the distance check regions have surfaces with a level equal to that of a reference surface of the wafer, or that the forming step includes a step of depositing a flat thin-film layer or flat thin-film layers on the distance check regions so that the distance check regions have surfaces with a level equal to that of a thin-film layer or thin-film layers deposited on the reference surface of the wafer.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.